Mattress



FIG. 1 is an top front perspective view of a mattress, showing my new design;

FIG. 2 is an top left rear perspective view thereof;

FIG. 3 is an top right perspective view thereof;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom view thereof. 

CLAIM The ornamental design for a mattress, as shown and described. 